1. Field of the Invention
The invention relates to a method for diagnosis of a capacitive actuator and an associated drive circuit, in particular, a piezoelectric actuator for a fuel injection valve, and a configuration for carrying out the method.
A method for driving an actuator is described in German Published, Non-Prosecuted Patent Application DE 196 44 521 A1. According to the method therein, a capacitive actuator is supplied with a predeterminable amount of energy by charge reversal of a charge-storage capacitor, which is charged to an initial voltage value, through a ringing coil to the actuator until the charge-storage capacitor has reached a predeterminable final voltage value. The amount of energy transmitted to the actuator is determined from the voltage difference between the initial voltage value and the final voltage value. Alternatively, the actuator current supplied to the actuator and the actuator voltage applied to the actuator are multiplied, the product is integrated, and the integral value is compared with a predeterminable nominal value. The charge-reversal process is interrupted when the integral value reaches or exceeds the nominal value.
2. Summary of the Invention
It is accordingly an object of the invention to provide a method and configuration for diagnosis of a capacitive actuator and of an associated drive circuit that overcomes the hereinafore-mentioned disadvantages of the heretofore-known methods and devices of this general type.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a method of diagnosing a capacitive actuator and an associated drive circuit, including the steps of transmitting a predeterminable amount of energy to an actuator from a charge-storage capacitor through a ringing coil, deducing a functional status of at least one of the actuator and an associated drive circuit from a discrepancy between reference values and at least one determined variable including actuator voltage, actuator current, and actuator charge, deducing a short-circuit of at least one of an electrical connection within the actuator and an electrical connection between the drive circuit and the actuator if the actuator voltage is less than a lower voltage value of the reference values, and deducing an interruption in at least one of the electrical connection within the actuator and the electrical connection between the drive circuit and the actuator if an actuator peak current is less than a lower current value of the reference values.
The invention is based on the idea that a drive circuit with a charge-storage capacitor and a ringing coil, which form a series tuned circuit together with the actuator, reacts in a predictable manner when faults that are typical of the actuator occur. For example, an actuator voltage measured across the actuator, an actuator current flowing through the actuator, or an actuator charge applied to the actuator can be used, by comparison with predetermined reference values, to deduce the functional status of the actuator and of the associated drive circuit.
In accordance with another mode of the invention, a serviceable functional status is deduced if the actuator voltage is between the lower voltage value and an upper voltage value of the reference values.
In accordance with a further mode of the invention, an excessively low actuator capacitance is deduced if the actuator voltage is greater than an upper voltage value of the reference values.
In accordance with an added mode of the invention, an interruption in at least one of the electrical connection within the actuator and the electrical connection between the drive circuit and the actuator is deduced if the actuator voltage is greater than a upper voltage value of the reference values.
In accordance with an additional mode of the invention, the actuator voltage is measured during a hold time.
In accordance with yet another mode of the invention, the actuator voltage is measure during a rise time, and a short-term interruption in the electrical connection within the actuator during a deflection process of the actuator is deduced if the actuator voltage is greater than an upper peak voltage of the reference values.
In accordance with yet a further mode of the invention, the actuator peak current is determined during a rise time as the maximum value of the actuator current.
In accordance with yet an added mode of the invention, a correct functional status is deduced if the actuator peak current is between a further lower current value of the reference values and an upper current value of the reference values.
In accordance with yet an additional mode of the invention, an excessively low actuator capacitance is deduced if the actuator peak current is less than a further lower current value of the reference values.
In accordance with again another mode of the invention, a short-circuit in at least one of the electrical connection within the actuator and the electrical connection between the drive circuit and the actuator is deduced if the actuator peak current is greater than an upper current value of the reference values.
In accordance with again a further mode of the invention, the actuator charge is determined from a charge-storage capacitor to the actuator during a rise time.
In accordance with again an added mode of the invention, a correct functional status is deduced if the actuator charge is between a lower charge value of the reference values and an upper charge value of the reference values.
In accordance with again an additional mode of the invention, an excessively low actuator capacitance is deduced if the actuator charge is less than a lower charge value of the reference values.
In accordance with still another mode of the invention, an interruption in at least one of the electrical connection within the actuator and the electrical connection between the drive circuit and the actuator is deduced if the actuator charge is less than a lower charge value of the reference values.
In accordance with still a further mode of the invention, a short-circuit of at least one of the electrical connection within the actuator and the electrical connection between the drive circuit and the actuator is deduced if the actuator charge is greater than an upper charge value of the reference values.
In accordance with still an added mode of the invention, the reference values are dependent on a temperature of the actuator.
In accordance with still an additional mode of the invention, a reaction to a fault is initiated after an occurrence of more than a predetermined number of faults of a given fault type within a predetermined fault time.
In accordance with another mode of the invention, a discrepancy between a value of the at least one determined variable of the actuator in a drive process from another value of the at least one determined variable of the actuator is determined in a subsequent drive process, and deducing a fault if the discrepancy exceeds a predetermined tolerance band.
With the objects of the invention in view, there is also provided a configuration for diagnosing a capacitive actuator and a drive circuit, including a drive circuit having a drive signal for controlling a drive process of the actuators, a charge-reversal circuit having, at least one charge-storage capacitor, at least one ringing coil, charge-reversal switches, diodes, and selection switches, and an energy source connected to the charge-reversal circuit, actuators having electrical connections, the actuators connected to the charge-reversal circuit, the actuators having actuator voltages, actuator currents, and actuator temperatures, the at least one charge-storage capacitor transmitting a predeterminable amount of energy to at least one of the actuators through the at least one ringing coil, a microprocessor-controlled controller connected to the drive circuit and to the actuators, the controller programmed to process the drive signal, the actuator voltages, the actuator currents, and the actuator temperatures, the controller having, a constant memory storing reference values including a lower voltage value and a lower current value, a logic unit producing control signals driving the charge-reversal switches and selection signals driving the selection switches for selection of the actuators, and comparators comparing at least one of the actuator voltages and the actuator currents with the reference values and producing comparison signals for the logic unit, the controller outputting a function signal representing a functional status based upon the comparison signals, and the controller programmed to deduce, a short-circuit of at least one of an electrical connection within one of the actuators and an electrical connection between the drive circuit and at least one of the actuators if one of the actuator voltages is less than the lower voltage value, and an interruption in at least one of an electrical connection within one of the actuators and an electrical connection between the drive circuit and at least one of the actuators if an actuator peak current is less than the lower current value.
In accordance with another feature of the invention, the controller has an analog/digital converter for receiving the actuator voltages and for outputting digitized values of the actuator voltages to the logic unit.
In accordance with a further feature of the invention, there is provided a peak value detector to determine a peak voltage of at least one of the actuators based upon at least one of the actuator voltages, the reference values including a predetermined upper peak voltage, and the controller having a peak value comparator comparing the peak voltage with the predetermined upper peak voltage and outputting a comparison result to the logic unit.
In accordance with an added feature of the invention, the reference values include lower voltage values and upper voltage values, and the controller has a voltage comparator comparing at least one of the actuator voltages with at least one of the lower voltage values and the upper voltage values and outputting a comparison result to the logic unit.
In accordance with an additional feature of the invention, there is provided a maximum-value forming device determining the actuator peak current from the actuator currents, the reference values including lower voltage values, upper voltage values, and an upper current value, the controller having a current comparator comparing the actuator peak current with the lower current value and the upper current value, and the controller programmed to output a comparison result to the logic unit.
In accordance with a concomitant feature of the invention, there is provided an integrator integrating at least one of the actuator currents over time to determine an actuator charge, the reference values including a lower charge value and an upper charge value, the controller having a charge comparator comparing the charge transmitted to at least one of the actuators with at least one of the lower charge value and the upper charge value, and the controller is programmed to output a comparison result to the logic unit
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and configuration for diagnosis of a capacitive actuator and of an associated drive circuit, it is, nevertheless, not intended to be limited to the details shown because various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.